Lubricating compositions



2,958,661 Patented Nov. 1, 1960 ice LUBRICATING COMPOSITIONS Thomas E. Reamer, El Cerrito, and John E. Weigel, Berkeley, Calif., assignors to Shell Oil Company, New York, N. Y., a corporation of Delaware No Drawing. Filed Feb. 24, 1958, Ser, No. 716,864

Claims. (Cl. 252-33.6)

This invention relates to aqueous base, metal-working lubricating compositions. More particularly, it relates to extreme pressure water-base metal cutting fluids for use in cutting, drilling, reaming and other machining and forming operations of ferrous and non-ferrous metals.

It is known that water-base cutting fluids possess good cooling properties, but that they lack the lubricating and extreme pressure properties of oil base lubricants. On the other hand, oil base lubricants are inferior Coolants and are costly.

The art discloses various water-base cutting fluids, most of which lack extreme pressure properties. Because of the multiplicity of additives which the bulk of such fluids contain, they are unstable, tend towards phase separation and foaming, and are difiicult and expensive to prepare. Among the materials commonly used in such water solutions are an alkali, e.g., borax, sodium carbonate or trisodium phosphate, an anti-rust agent, e.g., sodium nitrite or triethanolamine, and wetting, buffering, solubilizing and load carrying agents. The latter class of additives.

are generally water-soluble non-ionic compounds such as a reaction product of alkylphenol-ethylene oxide or a block polymer of ethylene oxide and propylene oxide sold commercially under the trade name of Pluronics (Wyandotte Chemical Company) It is an object of this invention to provide a metalworking aqueous base lubricant having both good cooling and good lubricating properties. Another, object of the invention is to provide a non-corrosive water-base cutting fluid. Still another objectof the invention is toprovide a stable water-base cutting fluid useful at high speeds, ele-,

vated temperatures, heavy loads andextreme pressures.

The above and other objects are attained by the present invention which provides a metal working lubricant of an aqueous medium, e.g., water containing from about 1% to about 10% of a water-soluble neutral polyalkali metal salt of a mercaptopolycarboxylic acid, preferably the sodium lithium or potassium tri-alkali metal salt of a mercaptoaliphatic dicarboxylic acid. By neutralized salt is meant the salt in which there is an equivalent of alkali metal for each acid equivalent, both mercapto and, car-. boxylic. The pH of the solution should be between 8 and 12.

Although the compositions are excellent for use in general machining operations, under extremely severe con ditions of speed, temperature and pressure it is desirable to add to the composition from about 1% to 20% of a hetero-copolymer of ethylene oxide and 1,2-propylene oxide as their monoand di-ether and ester derivatives of monohydric alcohols and of monocarboxylic acids, in which the polyoxy alkylene constitutes the major part of the product and having an average molecular weight of at least about 250 and usually below 1500.

The combination of the water-soluble polyalkali metal salt and the water-miscible hetero-copolymeric ethylene oxide 1,2-propylene oxide is unique. The latter compounds activate the extreme pressure properties of the salts whereas other non-ionic compounds such as a reaction product of alkylphenol-ethylene oxide or block copolymers of ethylene oxide and propylene oxide are either ineffective in activating the polyalkali metal salts or produce a detrimental effect such as foaming or solution instability.

The water-soluble polyalkali metal salts of mercaptopolycarboxylic acids are illustrated by tri-sodium, trilithium and tri-potassium salts of mercaptoaliphatic polycarboxylic acids, such as mercaptomalonic acid, mercaptosuccinic acid, mercaptoglutaric acid, mercaptoadipic acid, mercaptosebacic acid and of mercaptoaromatic polycarboxylic acids, such as mercaptophthalic acid and mixtures thereof. The mercapto radical can be alpha or beta to a carboxylic acid radical and preferably alpha to it. The acid portion of the salt may contain short alkyl radicals of from 1 to 4 carbon atoms as for instance, 2-methyl-2- mercaptosuccinic acid, 3-methyl-2-mercaptosuccinic acid, Z-methyl-Z-mercaptoadipic acid, S-methyl 2 mercaptoadipic acid, 3-methyl-4-butyl-2-mercaptoadipic acid and mixtures thereof. The tri-sodium and tri-lithium salts, e.g., trisodium and trilithium 2-mercaptomalonates and trisodium and trilithium 2-mercaptosuccinates are preferred.

The water-miscible hetero-copolymer polyalkylene oxide fluids which activate the above salts are heterocopolymers of ethylene oxide and 1,2-propylene oxide, as well as monoethers and monoesters thereof, preferably at oxide ratios of from :25 to 10:90 ethylene oxide to 1,2- propylene oxide, and molecular weight of from about 250 to about 1500.

By a ratio of from 75:25 to 10:90 is meant that, in the oxide used to form the copolymer the amount of 1,2- propoylene oxide in the mixture is. from /3 to 9 times the amount of ethylene oxide present, by weight, the parts or proportion of the 1,2-propylene oxide being given last. These materials are described in U.S. Patents 2,425,755 and 2,425,845. The modified copolymer diols may be employed or the monoethers or monoesters thereof may be used. In the preparation of the monoethers, alcohols having from 1 to about 10 carbon atoms are preferred, preferably aliphatic monohydric alcohols, while in the preparation of monoesters, monocarboxylic acids having from 1 to 12 carbon atoms are preferred, preferably C C fatty acids.

The following compositions are representative compositions of the invention which can be used neat or diluted with from 1 to 20 parts of water, as metal-working lu+ Hetero-copolymer of ethylene oxide-1,2-propylene oxide (7.5/25) having a viscosity of 450 at 100 F. 10

Water Composition C Trisodium mercaptomalonate SNa Composition D Percent Tripotassium mercaptosuccinate (KSCH-COOK) CHZCOOK 5 Water 95 Composition E Trisodium mercaptomalonate 5 Hetero-copolymer of ethylene oxide-1,2-propylene oxide (75/25) having a viscosity of 450 at 100 F. 10 Water 85- Composition F Trisodium 2-methyl-2-mercaptoadipate SNa (NaO o(oH)3ho 0 ONE) Hetero-copolymer of ethylene oxide-1,2-propylene oxide (75/25) having a viscosity of 1400 at 100 F Water 90 Composition G Tripotassium mercaptosuccinate 5 Hetero-copolymer of ethylene oxide-1,2-propylene oxide having a viscosity of 450 at 100 F 10 Water 85 Composition H Trisodium mercaptosuccinate 5 Disodium acid phosphate 1 Water 94 Composition I Trisodium mercaptosuccinate 5 Hetero-copolymer of ethylene oxide1,2-propylene oxide (75/25) having a viscosity of 490 at 100 F. Disodium acid phosphate 2 Water 7 83 Composition J Trisodium mercaptosuccinate 5 Hetero-copolymer of ethylene oxide 1,2-propylene oxide (75/25) having a viscosity of 490 at 100 C. 10 Sodium chromate 2 Water 83 Composition K Trilithium mercaptosuccinate (LiSCH-COOLl omoooLi) '5 Water 95 Composition L Trilithium mercaptosuccinate 5 Hetero-copolymer of ethylene oxide-1,2-propylene oxide (75/25) having a viscosity of 450 at 100 F. 10 Water 85 w l CompositionM Disodium-potassium mercaptosuccinate .(KSCH-COONa) GHr-COONa 5 Water 95 The outstanding properties of compositions of this invention were demonstrated by subjecting them to the following tests:

(1) Four-Ball Machine Test as described in the Journal of the Institute of Petroleum Technology, pages 206-229, April 1946.

(2) Drilling Test: The compositions were used in drilling deep 1" holes in AISI 4340 steel at 1440 rpm. and compared with a reference water base cutting fluid (X), said fluid being rated as Compositions A-M in the Four-Ball Test gave average weld loads in kgm. of between 600-1000. Compositions A, C, D, H, K and M gave values of 280% while Compositions B, E, F, G, I and L gave values of 540% above the reference fluid (X). The test results show, i.a., the advantage of incorporating the copolymer in the compositions. The substitution of other salts of sulfurcontaining carboxylic acids for the polyalkali metal mercaptopolycarboxylates used in compositions of this invention (AM) such as sodium mercaptoacetate or sodium dodecylthiosuccinate or sodium thiodiglycolate or sodium thiodipropionate or sodium dibutyl-dithiocarbamate gave weld loads in the Four-Ball Machine of around 200-300. Also, the substitution of other types of non-ionic compounds for the hetero-copolymer used in Compositions B, E, F, G, I and L such as a block copolymer of ethylene oxide and propylene oxide available commercially under the trade name Pluronic L64 (Wyandotte Chemical Company) or alkylphenol-ethylene oxide condensation product caused excessive foaming whereas the compositions of the present invention containing the hetero copolymer are non-foaming.

Compositions of this invention can contain additional additives water-soluble corrosion inhibitor, e.g., inorganic chromates, phosphates such as alkali metal phosphates and chromates, e.g., Na or K acid phosphates or chromates, perfuming agents, dyes and may be applied with excellent results to general cutting operations where cooling and lubricating of the tool and Work piece under adverse conditions are encountered. Metals machined with the aid of fluids of this invention have good surface finish, are free from rust and the tool life is excellent.

We claim as our invention:

1. An aqueous metal-working lubricant comprising a major amount of water and from about 1% to about 10% by weight of water-soluble tri-alkali metal salt of a mercaptodicarboxylic acid wherein the mercapto radical is attached to a carbon atom selected from the group consisting of carbon atoms which are in the alpha and beta positions to a carboxyl group and from about 1% to about 10% by weight of a water-miscible hetero-copo1y-. mer of ethylene oxide and 1,2-propylene oxide wherein' the ethylene oxide and 1,2-propylene oxide are combined in the weight ratio of 75:25 to 10:90, respectively, and wherein the copolymer has a molecular weight 0 from about 250 to 1500.

2. An aqueous metal-working lubricant comprising a major amount of water and from about 1% to about 10% by weight of Water-soluble trisodium salt of a saturated aliphatic mercaptodicarboxylic acid wherein the mercapto radical is attached to a carbon atom selected from the group consisting of carbon atoms which are in the alpha and beta positions to a carboxyl group and from about 1% to about 10% by weight of a water-miscible heterocopolymer of ethylene oxide and 1,2-propylene oxide wherein the ethylene oxide and 1,2-propylene oxide are combined in the weight ratio of 75 :25 to 10:90, respectively, and wherein the copolymer has a molecular weight of from about 25 0 to 1500.

3. An aqueous metal-working lubricant comprising a major amount of water and from about 1% to about 10% by weight of water-soluble tripotassium salt of a saturated aliphatic mercaptodicarboxylic acid wherein the mercapto radical is attached to a carbon atom selected from the group consisting of carbon atoms which are in I the alpha and beta positions to a carboxyl group and from about 1% to about by weight of a watermiscible hetero-copolymer of ethylene oxide and 1,2- propylene oxide wherein the ethylene oxide and 1,2- propylene oxide are combined in the weight ratio of 75:25 to 10:90, respectively, and wherein the copolymer has a molecular weight of from about 250 to 1500.

4. An aqueous metal-working lubricant comprising a major amount of water and from about 1% to about 10% by weight of water-soluble trilithium salt of a saturated aliphatic mercaptodicarboxylic acid wherein the mercapto radical is attached to a carbon atom selected from the group consisting of carbon atoms which are in the alpha and beta positions to a carboxyl group and from about 1% to about 10% by weight of a water-miscible heterocopolymer of ethylene oxide and 1,2-propylene oxide wherein the ethylene oxide and 1,2-propylene oxide are combined in the weight ratio of 75:25 to 10:90, respectively, and wherein the copolymer has a molecular weight of from about 250 to 1500.

5. An aqueous metal-working lubricant comprising a major amount of water and from about 1% to about 10% by weight of water-soluble trisodiurn mercaptosuccinate and from about 1% to about 10% by weight of a watermiscible hetero-copolymer of ethylene oxide and 1,2- propylene oxide wherein the ethylene oxide and 1-2- propylene oxide are combined in the weight ratio of 75:25 to 10:90, respectively, and wherein the copolymer has a molecular weight of from about 250 to 1500.

6. An aqueous metal-working lubricant comprising a major amount of water and from about 1% to about 10% by weight of water-soluble trisodium mercaptomalonate and from about 1% to about 10% by weight of a water-miscible hetero-copolymer of ethylene oxide and 1,2-propylene oxide wherein the ethylene oxide and 1,2-propylene oxide are combined in the weight ratio of 75:25 to 10:90, respectively, and wherein the copolymer has a molecular weight of from about 250 to 1500.

7. An aqueous metal-working lubricant comprising a major amount of water and from about 1% to about 10% by weight of water-soluble tripotassium mercaptosuccinate and from about 1% to about 10% by weight of a water-miscible hetero-copolymer of ethylene oxide and 1,2-propylene oxide wherein the ethylene oxide and '1,2propylene oxide are combined in the weight ratio of :25 to 10:90, respectively, and wherein the copolymer has a molecular weight of from about 250 to 1500.

8. An aqueous metal-working lubricant comprising a major amount of water and from about 1% to about 10% by weight of water-soluble trilithium mercapto succinate and from about 1% to about 10% by weight of a water-miscible hetero'copolymer of ethylene oxide and 1,2-propylene oxide wherein the ethylene oxide and 1,2-propylene oxide are combined in the weight ratio of 75:25 to 10:90, respectively, and wherein the copolymer has a molecular weight of from about 250 to 1500.

9. An aqueous metal-working lubricant comprising a major amount of water and about 5% by weight of trisodium mercaptosuccinate and about 10% by weight of a hetero-copolymer of ethylene oxide and propylene oxide combined in the weight ratio of 75 :25 respectively and having a viscosity of 450 centistokes at F.

10. An aqueous metal-working lubricant comprising a major amount of water and about 5% by weight of trilithium mercaptosuccinate and about 10% by weight of a hetero-copolymer of ethylene oxide and propylene oxide combined in the weight ratio of 75:25 respectively and having a viscosity of 450 centistokes at 100 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,363,512 Farrington et al Nov. 28, 1944 2,426,496 Farley Aug. 26, 1947 2,581,512 Chilcote Jan. 8, 1952 FOREIGN PATENTS 716,354 Great Britain Oct. 6, 1954 OTHER REFERENCES Iour. of Biological Chem, vol. 63, 1925, page 92. 

1. AN AQUEOUS METAL-WORKING LUBRICANT COMPRISING A MAJOR AMOUNT OF WATER AND FROM ABOUT 1% TO ABOUT 10% BY WEIGHT OF WATER-SOLUBLE TRI-ALKALI METAL SALT OF AMERCAPTODICARBOXYLIC ACID WHEREIN THE MERCAPTO RADICAL IS ATTACHED TO A CARBON ATOM SELECTED FROM THE GROUP CONSISTING OF CARBON ATOMS WHICH ARE IN THE ALPHA AND BETA POSITIONS TO A CARBOXYL GROUP AND FROM ABOUT 1% TO ABOUT 10% BY WEIGHT OF A WATER-MISCIBLE HETERO-COPOLYMER OF ETHYLENE OXIDE AND 1,2-PROPYLENE OXIDE WHEREIN THE ETHYLENE OXIDE AND 1,2-PROPYLENE OXIDE ARE COMBINED IN THE WEIGHT RATIO OF 75:25 TO 10:90, RESPECTIVELY, AND WHEREIN THE COPOLYMER HAS A MOLECULAR WEIGHT OF FROM ABOUT 250 TO
 1500. 